The pleas for help range from the unintentionally comical (“live chicken poultry place, strong foul odor in the air”) to eerily evocative (“the smell comes mostly at night — been like this all summer”) to inescapably common (“smells like rotten eggs”). But however you read the city of Chicago’s odor complaints, one thing is clear: The city stinks.

This is never more apparent than on hot summer days. We practice shallow breathing while packed into “L” cars, cross the street to avoid those mysterious “stink corners.” It’s the one time it’s nice to be second to New York City — everybody knows they outrank us in summertime stench.

Then again, maybe we’re all just being closed-minded when it comes to smells. What if we smelled without judgment, but with curiosity and a sense of discovery? What if, instead of scuttling down a rote set of streets on your daily rounds, you could smell your way to work?

Scientists and researchers say you can — which is why they’re looking at how smells have shaped cities, and working to create smell maps of cities around the world.

“Smells form a significant component of human knowledge about local environments,” says Kate McLean, program director in graphic design at Canterbury Christ Church University in the U.K., in an email interview. “Smells act as markers of change (diurnal, seasonal ...), as ambiance and also act as personal markers of place-indexing activity. Smells are both a survival tool (smoke, escaping gas, burnt toast) and an element of emotional relationships with place (seaside, pine forests, souks).”

McLean is a smell collector, someone who routinely sticks her nose into, say, dog fur or a random hedge, just to catch a scent. She began studying smells as a part of an alternative way to know the city of Edinburgh, Scotland, while pursuing her Master of Fine Arts there. “I started deconstructing the city through sensory approaches,” she says, “and representing the findings as maps which deliberately withheld information and encouraged the map reader to actively experience for themselves.”

Cities, she quickly realized, were a rich stew of smells.

“The first smells I was curious about were those encountered in the contemporary city. In the case of Edinburgh, they included brewery fumes, penguins at the zoo, fish and chip shops, cut grass, cherry blossom.” McLean developed a method of “smell walking” (which includes both heavy sniffing and actually sticking your nose close to things to seek out smells) through city neighborhoods to document odors, then plotting that data on maps, which she presents in colorful, artistic renderings.

Jose M. Osorio / Chicago Tribune

A residential area looking west on West Superior Street at North Racine Avenue near the Kennedy Expressway was tagged with the "emissions" smell on an online map of city smells.

A residential area looking west on West Superior Street at North Racine Avenue near the Kennedy Expressway was tagged with the "emissions" smell on an online map of city smells. (Jose M. Osorio / Chicago Tribune)

He and colleagues Luca Maria Aiello, also of Nokia Bell Labs, and Rossano Schifanella, a professor at the University of Turin, create smell maps of cities using data mining. Specifically, they use a set of words that have been recognized by scientists as language that humans use for smells, then cross-reference that with geolocated social media posts and come up with maps that tie reports of smells to physical streets, blocks and neighborhoods in cities around the world.

“There are devices which can measure particles in the air,” says Quercia, “but this is complementary. Devices give you a number, but what social media can give you is another layer to that number, an emotional reaction.” So scientists will one day be able to know, for instance, the exact particle threshold of emissions from a factory that will tip the scale from “Hmm, weird smell” to “That stench is searing my brain. Call somebody!”

The somebody on the other end of those calls in Chicago is Dave Graham, the city’s assistant commissioner for environmental permitting and inspections. Graham’s department investigates odor complaints made by citizens of our city — sometimes as few as nine per month (in the winter) to more than 20 per month in the summer.

Most of the calls are voicing concern about industrial smells: petroleum, chemicals, spray paint, smelly smoke billowing down an alleyway, sewer gas. City inspectors follow those complaints like smell detectives, trying to chase down the source and make sure there’s no public health hazard or code violation.

“They’re going to have to poke around, snoop around and figure out what’s causing it,” says Graham. “Sometimes, these odors, you don’t necessarily find the source.” If it’s a really tough case, Graham, who is a former environmental consultant, might have to come out and take a look himself, though he notes his own sense of smell is less than sensitive. “The only thing that bothers me is my wife’s hand lotion. I don’t know why, but it drives me crazy.”

Many of the smells Graham’s team investigates turn out to be “more of a nuisance issue” than a public danger, he notes. But smells and health concerns have been linked in the human mind for centuries. In fact, early worries about smells helped shape Chicago into the city it is today, says Melanie Kiechle, an urban smell historian and author of “Smell Detectives: An Olfactory History of Nineteenth-Century Urban America.”

Kiechle chose Chicago as one of the major subjects of her research, she says, partly because “Chicago definitely stunk.” The rapid rise of the meatpacking industry in the city, combined with explosive urban growth that outstripped the capacity for public sanitation, created a ready environment for a world of heady scents. “It was what we call a ‘shock city’” says Kiechle, “and not just because its growth was a shock to the environment, but also because when people arrived, they were literally shocked by the conditions.”

Obviously, we had a long way to go before the architectural boat tour made the town safe for tourists.

Nineteenth-century Chicagoans, Kiechle says, paid a lot of attention to smells. “People believed that bad airs caused disease. They called them miasmas. And one of the ways they knew the air was bad was the way it smelled.”

Germ theory didn’t rear its reasonable, scientific head until late in the 19th century, so Chicago’s citizens had to rely on their noses to tell them that something nasty might be brewing. Then, as now, laws allowed for citizens to complain about public nuisances and ask the city to regulate industry to tamp down the smells. Eventually, after some political maneuvering and a whole lot of citizen complaints, the “Stink Trials” of the 1870s marked the first time courts ordered the regulation of powerful packing houses and fat renderers until they agreed to install odor controls.

Odor, Kiechle says, also influenced another major historical moment: the decision to reverse the flow of the Chicago River. “Today we think that it was to protect the city’s drinking water,” Kiechle says, “and that was true, but they didn’t understand that in the 19th century. In 1865, when the project was started, the point of redirecting the water flow was to direct the stench of the water away from the city.”

Jose M. Osorio / Chicago Tribune

Pedestrians walk on East Ontario Street in Chicago on July 25, 2018. This part of the River North neighbrhood was tagged in an online map for the "food" smell.

Pedestrians walk on East Ontario Street in Chicago on July 25, 2018. This part of the River North neighbrhood was tagged in an online map for the "food" smell. (Jose M. Osorio / Chicago Tribune)

Basically, it worked: Today, on Quercia’s smell map of Chicago, the predominant smell reported along the riverwalk is “nature.” Depending on how close you’re standing to Lower Wacker Drive or Island Party Hut, the smell of nature might vary. But the beauty of tracking smells, Quercia says, is that you can choose which part of the riverwalk you’d prefer to walk down, based on scent. “If you see that a certain street smells like the poo of dogs,” he says, “you might go another way.”

In the future, Quercia and his team hope that urban planners might be able to put their data to good use to make cities smell better and, since smells are closely tied into the emotional centers of the brain, even less stressful.

“If you are placing a bench for people to sit and relax,” he says, “maybe you want to include plants with a restful smell, like lavender.” Until then, you can have a little fun by walking to the train by way of, say, baked goods rather than car emissions.

Or, like McLean, you can start to explore the city via smells. She has created a downloadable smell walk kit, that explains how to use specific techniques to both passively and actively catch and document smells as you go. “Participants leave with a new understanding of their city,” she says.

And maybe a little more acceptance. “Odors are odors,” says Graham. “You’re in the city, you’re smelling maybe the restaurant on the corner, a car shop, a nail salon, whatever.” On his own commute, he says, “I pass one building, and every so often I catch a whiff of something really bad.” Diagnosis? “It’s just the sewer. It might be something decomposing down there.”